import re
from django.core.management.base import BaseCommand
from imagekit.registry import generator_registry
from common.tasks import generate_thumbs_by_id_task


class Command(BaseCommand):
    help = ("""Generate files for the specified image generators (or all of them if
none was provided). Simple, glob-like wildcards are allowed, with *
matching all characters within a segment, and ** matching across
segments. (Segments are separated with colons.) So, for example,
"a:*:c" will match "a:b:c", but not "a:b:x:c", whereas "a:**:c" will
match both. Subsegments are always matched, so "a" will match "a" as
well as "a:b" and "a:b:c".""")
    args = '[generator_ids]'

    def handle(self, *args, **options):
        generators = generator_registry.get_ids()

        if args:
            patterns = self.compile_patterns(args)
            generators = (id for id in generators if any(p.match(id) for p in patterns))

        for generator_id in generators:
            self.stdout.write('Validating generator: %s\n' % generator_id)
            generate_thumbs_by_id_task.delay(generator_id)

    def compile_patterns(self, generator_ids):
        return [self.compile_pattern(id) for id in generator_ids]

    def compile_pattern(self, generator_id):
        parts = re.split(r'(\*{1,2})', generator_id)
        pattern = ''
        for part in parts:
            if part == '*':
                pattern += '[^:]*'
            elif part == '**':
                pattern += '.*'
            else:
                pattern += re.escape(part)
        return re.compile('^%s(:.*)?$' % pattern)
